Verify: add verify function for k8s Jobs

[pit1sIBM]

Related Issue

Supports #65

Related PRs

This PR is not dependent on any other PR

What this PR does / why we need it

Adds a default verify check for k8s Jobs

Special notes for your reviewer

If applicable**

• this PR contains documentation
• this PR contains unit tests
• this PR has been tested for backwards compatibility

What gif most accurately describes how I feel towards this PR?

[gabe-l-hart]

@pit1sIBM Thanks for the PR! It occurs to me that there may be several uses for a Job during a rollout:

1. Start a process that should not block further rollout
2. Start a process that should block further rollout

This PR clearly tackles (2), but I'm wondering if there's any realistic usecase for (1) that we should consider?

[pit1sIBM]

Thanks @gabe-l-hart, I'm of the mindset that any Job I create is one I expect to complete successfully. If I just want a process to run, I'd probably just create a Pod. So I would prefer Jobs to prevent further rollout since a failure is usually not desired.

I'm still wrapping my head around oper8 in general, but I assume if we wanted to merge this PR and still handle (1), we'd need to override the verify function in our own components to essentially revert the change I'm making here (and only check that the resource exists?)

[HonakerM]

@pit1sIBM thank you for opening this PR! We've needed a default job verification function for a while.

I'm of the mindset that any Job I create is one I expect to complete successfully

I think that makes sense as it's the safest approach.

I'm still wrapping my head around oper8 in general, but I assume if we wanted to merge this PR and still handle (1), we'd need to override the verify function in our own components to essentially revert the change I'm making here (and only check that the resource exists?)

Correct that's what you'd have to do now. However, I've been thinking about this more and we might want to add a verify_function argument to Component.add_resource similar to add_dependency to allow customizing per resource verification without overriding the entire verify. I'll open a PR with what I have in mind.

[gabe-l-hart]

Makes sense to me! @HonakerM Thanks for tackling that verify_function addition. With that, I think this is a great default to have.